Clarification needed on geological terminology


As has been reported in previous issues of the Timberjay, Highway 169 to Ely is being considered for reconstruction by the Minnesota Department of Transportation to address existing roadway condition and identified geometric design and safety issues. The Natural Resources Research Institute at the University of Minnesota Duluth (NRRI) was hired by MnDOT to conduct a geological survey of two possible realignment corridors in the vicinity of Eagles Nest Lake. Information regarding NRRI’s mapping of bedrock outcrops along the “North Route” and “South Route” relocation alignments considered for Minnesota Highway 169 needs clarification. A number of statements made by others in the May 15, 2013, article by Timberjay Editor Marshall Helmberger are out of context from our work and confuse the results of our two reports to MnDOT (both reports are available online at We hope this letter clarifies information discussed in the May 15 article that is presented in our reports.

Geological mapping was conducted by finding outcrops and locating their geographic positions with a handheld GPS, identifying the rock type(s), collecting samples, and making a visual estimate of the percent of sulfide minerals present. A representative sample(s) was collected with a hammer; a drill coring device was used in few places where sampling by hammer was not feasible. The visual estimate of sulfide minerals included an overall estimate for the outcrop, as well as estimates of any zones on the outcrop that contain higher visual percentages than the outcrop as a whole. These anomalous sulfide mineral-bearing zones were described as to their size, how they occurred in the outcrop, and a visual estimate for the percent sulfide present was made. Later discussions with MnDOT, the Minnesota Pollution Control Agency, and Minnesota Department of Natural Resources led to geochemical analysis of the sulfur content of 94 random samples and 66 sulfide mineral-bearing samples by a commercial laboratory. All the samples analyzed chemically came from the rocks that surround the proposed road cuts along the “South Route.”

In the May 15 article, an official from the MDNR is quoted as saying “Ten out of the set of 66 samples in or near the road cuts have chemical assays of 0.30 percent-weight [sic] or more sulfur, which would be classified into a higher mitigation class.” These samples are only from the visually estimated sulfide mineral-rich samples, of which 13 actually contain greater than 0.30 weight-percent sulfur. This mischaracterization of the information from the NRRI report disregards 94 random samples taken from the same area, only focusing on those from the smaller sulfide mineral-rich group. When looking at the chemistry of all the samples, only 15 of 160 samples (~9%) contain more than 0.30 weight-percent sulfur. Furthermore, many of the samples containing elevated sulfur contents are from small parts of larger outcrops that had significantly lower sulfur. There are indeed areas that need further investigation with drilling and testing, but they are localized and do not represent the majority of the rocks in the area under consideration for excavation.

The article also quotes the MDNR official as saying that the “sulfide intrusions into the surrounding greenstone are ‘steeply-dipping’ which makes it harder to determine how extensive the intrusions might be.” When contacted, that official has no recollection of making any comment about “sulfide intrusions.” The fact is there are no “sulfide intrusions” in the area under discussion. While the rocks are steeply dipping in the area, making it difficult to exactly know where something may be under the surface, the nature of sulfide occurrences in the veins and beds make it possible to generally predict that their distribution in the shallow subsurface will be similar to what is seen at the surface where outcrops are present.

The higher sulfur rocks are not distributed evenly through all of the rock, but generally occur in thin fractures and beds in the rocks along the “South Route.” The rocks exposed at the surface contain low abundances of sulfide minerals, and, only in small areas, do they exceed the 0.30 weight-percent sulfur values. Contrary to the quote attributed to the EPA’s Kenneth Westlake in the article, there are no “sulfide ore outcrops” along the “South Route.”

To further clarify, the samples with sulfur analyses come from the “South Route” alignment. The “North Route” was removed from consideration because many of the rocks mapped in that area had much higher visual sulfide mineral percentages than rocks along the “South Route.” The sulfide mineral-bearing zones were more evenly distributed through “North Route” rocks than “South Route” rocks. Also the “North Route” would have likely disturbed wetlands that are suspected of being underlain by rocks containing higher percentages of sulfide minerals based on results from investigating four drill holes located just to the west of the area.

I would welcome further questions regarding our findings or clarification of the details of our research.

John Heine P.G.

UMD Natural Resources

Research Institute

Duluth, Minn.

Editor Responds:

I would certainly never pretend to be a geologist, which is why in reporting on this issue, I have referred to the work of actual geologists, such as John Heine of NRRI or Dennis Martin, from the Minnesota Department of Natural Resources, who has drafted detailed comments on NRRI’s findings.

Mr. Heine points out that I used some technical geological terms incorrectly. Words such as “ore” and “intrusion” have specific definitions to geologists that are not always apparent to non-geologists such as myself. I apologize for any imprecision and thank Mr. Heine for the clarification.

Unfortunately, none of what Mr. Heine goes to great length to discuss pertains in any significant way to the story to which he refers.

Our May 15 story on this topic was sparked by a press release from the office of Congressman Rick Nolan, which alerted constituents that he had chastised the federal Environmental Protection Agency for its comment letter to MnDOT regarding the Hwy. 169 reconstruction project, which raised (among other issues) concerns about the presence of sulfide minerals in the area and the potential for acid rock drainage if significant amounts of such material were exposed during highway reconstruction. In that release, Rep. Nolan wrote that the federal agency had cited “no scientific evidence of any documented dangers, referring only to “potential” adverse effects that “might” result as rock and soil are moved.”

At the time, this struck me as an unusual claim, since having reported on this issue for some time, I was well aware that the sulfide issue was not a figment of the EPA’s imagination. Mr. Heine acknowledges that sulfide minerals were indicated in both the proposed northerly and southerly realignments. Indeed, MnDOT officials working on the project had already determined that additional analysis would be done to better understand the sulfide concerns. EPA’s letter simply asked for the same.

I contacted Nolan’s press office and asked a very obvious question, which no other reporters apparently bothered to ask. Why chastise the EPA for comments very much in line with those of state geologists and even MnDOT officials? Those are exactly the kind of questions reporters should ask.

The response from Nolan’s office was eye-opening to say the least. It’s rather long, which prevents me from printing it in its entirety, but I will post the entire response online.

But the most relevant comments were these:

“No mention was made to Congressman Nolan regarding any official or unofficial involvement, analysis or comments by NRRI or Minnesota DNR concerning the sulfide issue and the route the task force had chosen.  MNDOT officials we have spoken to were also unaware of any comments. 

“As presented to Congressman Nolan, the concern of the Task Force was that after all the work of qualified local authorities, an opponent of the project filed a complaint with the EPA. The agency then elected to comment on the project.  The simple assertion by the EPA that sulfide could potentially be a problem, without providing any evidence of such a threat, had a substantial impact on the state agencies and the direction of the project.

“…It is unlikely that the sulfide pollution associated with the 169 project...would result in significant environmental impact.  In this respect, it is an over reach by EPA to insert themselves into these local issues, and it is careless of them to do so without taking into account the broad public interest.”

This response immediately alerted me that the Congressman’s aides had failed to do their homework. Allowing the Congressman to take a highly public position criticizing a federal regulatory agency without realizing that state and regional experts shared the very concerns expressed by the federal regulators was reckless. What’s worse, MnDOT had previously supplied the Congressman’s office with a copy of the NRRI technical report on the sulfide issue. Apparently no one in Rep. Nolan’s office bothered to read it.

It’s no secret that the EPA is a favorite whipping boy for our area’s politicians, and sometimes the EPA deserves it. But, at least when it comes to the Hwy. 169 project, it really does not appear that the agency was out of line.

Further, to suggest that an opponent had filed a complaint with the EPA may also be in error. I asked Nolan’s office for a copy of any such complaint, but they did not respond. The suggestion by Nolan’s staff that the EPA then “elected to comment” on the project after receiving a complaint is flat out wrong. EPA was a cooperating agency on the project from the beginning and MnDOT requested their comments as part of the process.

Perhaps most troubling was the claim by Nolan’s office that the Hwy. 169 project is “unlikely” to have any significant environmental impact. Fortunately, that’s not a question that’s left to the politicians to answer, because they don’t have a clue. Those issues are appropriately left to the technical experts, and at this point they all seem to agree that further analysis is needed before anyone can reasonably determine the significance of any environmental impact associated with the excavation of sulfur-containing pyrite in that vicinity.

I should mention that the NRRI geologists did not analyze sulfide risks along the existing Hwy. 169 alignment. Hopefully, a similar analysis will take place along that route as well, as part of the environmental review process.



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